The invention relates to a transducer-protector device for medical apparatus, useful in particular for protecting medical apparatus from contamination by infectious agents.
Specifically, though not exclusively, the invention can be advantageously applied in an apparatus for extracorporeal blood treatment, in particular a dialysis machine for treatment of kidney failure.
In particular, the invention relates to a transducer-protector device comprising a hollow housing body having two opposite openings, one for communication with an extracorporeal circuit and the other for communication with an operative unit of the medical apparatus, for example a device for measuring pressure in the extracorporeal circuit. The device comprises a barrier, in the form of a membrane, arranged in the housing body between the two openings.
The device of the invention functions both as a transducer, being able to transmit the pressure from one opening to the other without determining any practically relevant drop in pressure, and as an aseptic barrier which protects the medical apparatus from infectious agents originating from the patient.
The prior art comprises various transducer-protector devices of the above-indicated type, described for example in U.S. Pat. No. 4,314,480, EP 0 652 018, U.S. Pat. Nos. 5,500,003, 6,086,762, 6,506,237 and EP 1 097 725.
These known devices, which are also commonly called “blood-catchers”, comprise a hollow housing body having two opposite openings, a membrane housed in the hollow body between the two openings, two opposite tubular connectors, one in fluid communication with a side of the membrane and the other in communication with the other side of the membrane. One of the two tubular connectors is destined to be connected to a fluid line of an extracorporeal blood fluid transport line. The other tubular connector is destined to be connected to a fluid line of an operative unit of a medical apparatus. This medical unit usually comprises a pressure gauge for detecting the pressure within the extracorporeal circuit.
The membrane, which is hydrophobic, defines an anti-contamination barrier which is gas-permeable. The two tubular connectors are in reciprocal gas communication through a fluid pathway comprising the internal cavity of the hollow housing body, while remaining septically insulated one from another along the fluid pathway, thanks to the hydrophobic membrane.
In this way the device allows transmission of the pressure from the fluid-transporting extracorporeal circuit to the pressure gauge, without any significant load loss, while at the same time protecting the operators, the medical apparatus and the surrounding environment, from the risk of contamination by pathogens originating from the fluid running in the extracorporeal circuit. The device can also protect the extracorporeal circuit, and therefore the patient, from the intrusion of extraneous bodies coming from the medical apparatus (dialysis machine).
The hollow housing body normally comprises a pair of half-shells made of a rigid plastic material (for example PETG, PP or PE) joined together by ultrasonic welding. A peripheral edge of the hydrophobic protective membrane (for example made of PTFE) is interpositioned between the two half-shells and held solidly in position there.
A first half-shell bears a first connector which is destined to connect solidly and fluid-sealedly with a flexible tube of the service line in fluid communication with a blood chamber of the extracorporeal circuit. Normally the first half-shell is made in a single piece with the first connector.
The second half-shell bears a second connector which is destined for solid fluid-sealed connection with a male seating situated on the dialysis machine and connected in turn to the pressure gauge. The second connector is generally a female Luer connector made in a single piece of rigid plastic with the second half-shell.
One of the problems of transducer-protector devices of this type is the risk of kinking of the flexible tube which is connected to the first connector and which leads to the blood chamber. Both the transducer-protector device and the blood chamber are positioned on the dialysis machine in predetermined zones and with predetermined and obligated arrangements and orientation. The flexible tube, in order to join up the transducer-protector device and the blood chamber, can be forced to follow a curved pathway, with sometimes changes of direction through relatively narrow angles and the consequent risk of kinking and therefore occlusion of the tube.
A further drawback is that there is a certain degree of difficulty in coupling the device to the seating on the machine, due in part to the rigidity of the device itself.
To obviate these drawbacks the prior art comprises a transducer-protector device having a part which is deformable in a transversal direction to the longitudinal axis of the actual device. The deformable part, which comprises the second female Luer connector, is manufactured in an elastically-deformable material (for example soft PVC), separately from the second half-shell, and is subsequently joined to the second half-shell, for example by gluing using cyclohexanone or another coupling system. The transversal deformability of the soft part made of PVC enables a flexion of the transducer-protector device and reduces the risk of kinking of the flexible tube, easing the coupling maneuver of the machine device.
A drawback of the above-described solution is however its complex build, since it is necessary to manufacture and assemble an extra part. Furthermore, the presence of a further coupling zone, constituted by the gluing zone between the PVC female Luer connector and the rigid-plastic half shell, increases the risk of seal loss which, in this case, might lead to errors or loss of pressure gauge reading.